As we know, there is a tendency toward small and/or slim things in the electronic world, but they are still expected to preserve the original functions or have the improved effectiveness. Referring to FIG. 1a, a carriage 110 of the conventional flatbed scanner 101 is integrally formed. A document 111 provides an optical signal after receiving a light generated from the light source 102. The optical signal is transmitted to a lens 107 through four reflectors (103, 104, 105, and 106) and is received by a charge coupled device (CCD) 108 to complete a scanning process. FIG. 1b is a top view of the conventional carriage. The conventional carriage belongs to a fixed type carriage which additionally occupies a space (having a span distance 112) when a scanning window 115 disposed on the carriage 110 is positioned on the start position 113 of the scanning area of the scanner 101. However, the space does not make any contribution to the scanning process, Therefore, the applicant attempts to decrease the space of the scanner by eliminating the unnecessary distance 112, but a document with the same length can be still scanned.